Electromagnetic interference radiation is generated by the use of DC motors regardless of whether these DC motors are commutated electronically or via brush rockers, the radiation having a negative influence, for example, on the operation of other electronic systems or hindering radio reception or radio communication. At the same time, the system itself is sensitive to interfering radiation from other electronic systems. It is thus common, particularly in the automobile industry, that the electromagnetic compatibility of electronic components must be proved. For this purpose, special interference-suppression circuits are used that are typically formed by a printed circuit board on which bypass capacitors and interference-suppression chokes are arranged which are connected through conductor paths. For the grounding of these electronic components, an earth contact must be made.
DE 10 2006 044 304 A1 describes an arrangement of an interference-suppression circuit in which two interference-suppression circuits and three bypass capacitors are used which are aligned with each other so that the electromagnetic field lines of a choke, which is connected with a terminal of the electric motor, are perpendicular to the electromagnetic field lines of a bypass capacitor that is connected with the same motor terminal. The connection to earth is realized either by soldering the opposite ends of the electric lines of the capacitors to the metal housing of the DC motor, or by clamping a nose, which is formed on a punched connecting line, between an end cap and the end plate of the DC motor.
DE 10 2009 010 424 A1 describes an electric motor for a motor vehicle aggregate having a printed circuit board on which choke coils and bypass capacitors are arranged as interference-suppression elements, the printed circuit board being arranged on the rear side of a plastic material body serving as a cover plate. The earth connection is formed by conductor paths potted in the plastic material body, which conductor paths are connected with the printed circuit board and are guided to connecting contacts that are connected with the metal housing, the connecting contacts having holes through which the screws protrude via which the connection between the connecting contacts and the ends of the conductor paths is made.
Producing an earth connection of the interference-suppression components with the known DC motors accordingly requires screwing or soldering the conductor paths to the housing of the DC motor. Clamping connections are possible in the known designs only if the end plate can serve as the earth connection, i.e., if it is electrically conductive.